A shooting that left a hospital case worker dead this week was ended after a doctor returned fire with his own weapon, according to authorities in eastern Pennsylvania.

The suspect, identified by officials as Richard Plotts of Upper Darby, Pa., was a psychiatric patient at Sister Marie Lenahan Wellness Center on the campus of Mercy Fitzgerald Hospital in Darby, near Philadelphia.

Plotts was escorted into the center Thursday by Theresa Hunt, 53, his case worker, who he allegedly shot and killed, according to Delaware County Dist. Atty. Jack Whelan, who spoke at a news conference after the incident.

Authorities initially reported that Plotts had been shot but it was unclear by whom. Police later revealed the attack was stopped by a psychiatrist, Dr. Lee Silverman.

A series of news conferences fleshed out details of the incident. After Plotts entered the center with Hunt, he got into a loud argument with her and Silverman, and again with Hunt in a private examination room, where staff members saw him draw a gun. The staffers then heard shots.

Silverman was able to draw his own firearm and return fire, Whelan told The Associated Press. The suspect was later tackled by staff.

Silverman was grazed by a bullet during the confrontation.

Both Silverman and Plotts were taken to the Hospital of the University of Pennsylvania. The doctor was treated and released, and the suspect underwent surgery.

Hospital employees had reported previous incidents between Plotts and hospital staff, although they said they had no indication that he was armed or dangerous when he arrived Thursday, authorities said.